Non-intrusive monitoring of a patient's oxygen level is well known in medical technology. It is conventional, for example, to fasten a sensor head incorporating a polarographic oxygen sensor to the skin of a patient through the medium of a fixation ring.
The fixation ring is normally attached to the patient's skin in a suitable location with an adhesive. The sensor head is releasably held in the ring and comprises an insulating matrix having an anode and a cathode embedded therein. The anode and cathode are electrically insulated from each other but exposed at an electrochemically active base surface.
An anion exchange resin electrolyte is encapsulated between an oxygen diffusion material in the form of a permeable membrane and the base surface. The membrane presses against the patient's skin and oxygen from the patient's system flows through it to be monitored by a system of which the sensor head-membrane-electrolyte assembly is a part.
After each use of a fixation ring and sensor head-membrane-electrolyte assembly for monitoring purposes the permeable membrane is removed and discarded. It is also conventional to discard the fixation ring since it is a very inexpensive component. The sensor head, on the other hand, is reused.
Before every use of a sensor head it must be refitted with a permeable membrane encapsulating a suitable amount of electrolyte. To this end it is conventional to provide the medical facility with mounting tools for mating a permeable membrane to the sensor head. The mounting tools require some expertise to use. The process is relatively laborious and time consuming.